1. Field of the Invention
The present invention relates generally to a linear reciprocating flux reversal permanent magnetic machine, and more particularly to a linear reciprocating flux reversal permanent magnetic machine in which stators are provided with air gap sections and interpole sections and magnets are inserted into a mover, thus having high efficiency and being easily manufactured.
2. Description of the Prior Art
In general, a Linear Oscillatory Actuator (LOA) refers to a motor that performs a linear reciprocating motion with a certain stroke at a specific frequency, and is reversely used as a linear generator.
Electromagnetic LOAs can be classified into various types according to a mover and the number of excitation coils. That is, the electromagnetic LOAs are classified into a moving coil type, a moving core type, a moving magnet type, and a moving field type according to a mover. Meanwhile, in order to increase the performance of such an electromagnetic LOA system, a cylindrical structure, a magnet with high energy density, a spring with compressibility under a resonating condition, and a single-phase power source with a constant control frequency are required.
In the case where a long stroke is needed in a low speed range, it is preferable to operate the LOA in a cycle of acceleration, constant velocity and deceleration. In contrast, in the case where a short stroke below 5 cm is needed, it is possible to operate the LOA with a square wave voltage because a cycle of acceleration and deceleration is needed during a reciprocating motion. However, the LOA has to be operated by a Pulse Width Modulation (PWM) inverter that outputs a variable frequency and a variable voltage so as to reduce the harmonic waves of output power and operate the LOA with a frequency and a stroke desired by a system.
As shown in FIG. 1, in the moving magnet type LOA, electromagnets that are excited by current are employed as stators 110 and a magnet is employed as a mover 120. If current flows in the coils 130 in FIG. 1, each stator 110 is magnetized to have an S pole and an N pole, so the mover 120 experiences repulsive and attractive forces and thrust is generated.
Recently, the efficiency of the linear reciprocating flux reversal Permanent Magnet (PM) machine is increased to about 85xcx9c93% within an output range of 100 Watts to several hundreds Watts, and the operation of the LOA is optimally performed when a mechanical resonating frequency coincides with a commercial power source frequency.
In the meantime, a mechanical spring, for example, a multiple flexure, used for the reciprocating motion of the mover allows the mechanical resonating frequency to coincide with the commercial power source frequency, and serves as a bearing at the end of the stroke and an energy storage device.
However, the conventional linear reciprocating flux reversal PM machine is disadvantageous in that a large weight is required to achieve the efficiency of 85xcx9c93%. In the case where the linear reciprocating flux reversal PM machine has a mechanical resonating frequency of 50 Hz and an amplitude of 20 mm, weight per unit power can range from 25 kg/kW to 30 kg/kW.
Additionally, in the conventional linear reciprocating flux reversal PM machine, the mover performs a high speed reciprocating motion, so the conventional linear reciprocating flux reversal PM machine is disadvantageous in that an adhesive part to fix the magnet to the mover can be easily removed from the mover or be damaged.
Additionally, if a motor is formed to have a cylindrical shape as shown in FIG. 1, the motor has an air gap in axial and radial directions of the mover 120, so coil flux flows to a yoke positioned outside the axis of the mover 120 and the inside of the mover 120 along the axis of the mover 120. Accordingly, a radial laminated core is employed as the mover 120 to reduce iron loss, so the conventional motor is disadvantageous in that its manufacture is difficult and its manufacturing cost is high.
Moreover, the mover 120 needs to be comprised of a magnet and an iron core to strengthen the mover 120. In this case, when the magnet is constructed to surround the circumference of the core as shown in FIG. 1, the weight of the mover is increased, so the conventional motor is disadvantageous in that the range of reciprocating frequencies is restricted to several Hz.
Accordingly, in order to solve the above problems occurring in the prior art, an object of the present invention is to provide a linear reciprocating flux reversal PM machine, which can be easily manufactured by using a rectangular laminated core instead of a cylindrical laminated core, and can prevent an adhesive part from being removed from a mover and being damaged and decrease the weight of the machine by disposing magnets in the mover instead of around the mover.
In order to accomplish the above object, the present invention provides a linear reciprocating flux reversal Permanent Magnetic (PM) machine, comprising: a pair of stators arranged to be opposite to each other, the stators each having two coils wound in opposite directions, and air gap sections and interpole sections alternately arranged on inside portions of the stator in a crosswise direction of the stator with the air gap sections of a first stator opposite to interpole sections of a second stator; a mover disposed between the stators to be reciprocated therebetween, the mover having one or more bar-shaped magnets longitudinally and vertically embedded therein; and means for returning the mover to an initial position thereof, the returning means being connected to one or both ends of the mover.
The air gap sections and the interpole sections are implemented by forming grooves on inside portions of the stators.
It is preferable that the magnets embedded in the mover are arranged so that their poles having the same polarities confront each other.
In addition, it is preferable that the stators are each provided at a center of an inside portion thereof with a center groove to form two inside sub-portions to both sides of the center groove, and the coils are wound around the two inside sub-portions of the stator in opposite directions, respectively.
In addition, it is preferable that the returning means is a return spring having elastic force.